Electric discharge tube



April 20, 1943. E. c. DENCH ELECTRIC DISCHARGE TUBE Filed March 14, 1940 2 Sheets-Sheet 1 April 20, 1943. EQDENCH 2 316,773

ELECTRIC DISCHARGE TUBE Filed March 14, 1940 2 Sheets-Sheet 2 fawn/Pa CHARLES 17am Patented Apr. 20, 1943 UNITED STATES PATENT OFFICE 2,316,773 ELECTRIC DISCHARGE TUBE Edward Charles Dench, South Orange, N. .l. Application March 14, 1940, Serial No. 323,946

3 Claims.

The present invention relates to electric-discharge tubes, and more particularly to tubes wherein thermally-responsive materials are utilized to effect electrical control in response to their heating by the discharge. The present application is filed in response to a requirement for division in application, Serial No. 261,786, filed March 14, 1939, which matured, on January 13, 19%2, into Letters Patent 2,269,442. The present application is accordingly restricted to an electric-discharge tube, as distinguished from an electric system claimed in the said Letters Patent.

An object of this invention is to provide a new and improved electric-discharge tube.

Other and further objects will be explained particularly pointed out hereinafter and will be in the appended claims.

The invention will now be more fully explained in connectionvwith the accompanying drawings, in which Fig. l is a longitudinal section, partly in elevation, of an electric=dlscharge tube embodying the invention, in preferred form; Figs. 2 and 3 are diagrammatic views showing the electric-discharge tube of the present invention connected into difierent circuits to illustrate the operation thereof; Fig. i is a view similar to Fig. 1 of a modification; and Fig. 5 is a circuit dia ram illustrating the operation of the tube illus trated in Fig. 4.

A gas or gaseous-discharge tube will be considered as distinguished from a high-wacuuin tube according as to whether it is intended that as, vapor or similar substance be presen the tube at a predetermined optimum pressure for the purpose of producing ionization, or that the gas be removed from the tube to the highest degree possible. larly to tubes embodying cold cathodes, such as are commonly associated with high-voltage, low-current gas-discharge devices.

The present invention deals specifically with a gaseous-discharge tube of the type characterized by cumulative ionization in a preferably inert gas, such asneon or argon or a mixture of the same, or other gases. Mercury vapor may be used, and has certain advantages and disadvantages.

It is a well-known fact thatthe breakdown This invention relates particutrodes, normally spaced in the containe a predetermined distance from one another. The cathode d comprises a bimetal stripwhich may, or may not, be coated with electron-emitting material, such as magnesium or other material of low work-function, thus lowering the breakdown voltage. The cathode t is shown fixedly supporting at its free end a contact member 2 for cooperating with a contact member :1 supported by an electrode member 3. The contact members i and 2 are designed to carry a comparatively large current. They need not be the Single contact members shown; a y combination of-make-and-breal; contact members, operated directly or indirectly by thermal action, as hereinafter described, may be used. They may be multiple, and open or closed, as well as internal or external to the tube. They may be insulated from the bimetal or other electrodes by which they are supported, and connected to external circuits by independent conductors.

The additional electrodes in the tube a may comprise an anode i, illustrated as a wire projecting from a glass supporting sleeve l5, and a grid or other control electrode 6, which may be constituted of a metal wire or a metal cylinder of perforated or mesh material surrounding or overlapping the anocle l. A glass sleeve 15 may be employed to permit locating the anode l in the center of the grid b, so that more effective control may be attained.

As diagrammatically illustrated in Fig. 2, showing one type 01 circuit into which the electricvoltage of a gas between a pair of electrodes vided with a thermostatic or thermally-responsive cathode t and a plurality of additional elecdischarge tube of the present invention may be connected, the cathode bimetallic strip 4 may be adjustably connected to the negative side of a resistor or potentiometer ill, supplied with energy from a battery 9 l. The anode 71 may be connected to the positive side of the resistor H! through a ballast resistor or other impedance element 9, so as to impress a suitable potential upon the anode l, suficiently positive with respect to the cathode to maintain a gaseous discharge in the tube. This potential may be higher than the breakdown potential between the grid and the cathode. The impedance sometimes be omitted.

The bias of the grid may be varied by varying a tap connection 29 of the grid d through an impedance d to the resistor ill, to cause the grid to control the flow and the energy of the electrons between the cathode 4i and the anode l and, therefore, the gas discharge. The grid should normally be adjusted to some intermeelement 9 may diate potential lower than the breakdown value I of controlling a between it and the cathode, so as to provide a fixed cathode-anode breakdown voltage, and so as normally to restrain the discharge from taking place.

The pressure of the gas in the tube is chosen so that the breakdown voltage between the grid and the anode I, attained by positioning the grid relatively near to the anode as compared with the distance from the cathode to the anode, shall be substantially higher than that between the cathode 4 and the anode I. The current in the anode circuit, when the discharge takes place, is relatively larger, as limited by the impedance 9, than the pre-discharge currents in the control-grid circuit. Upon adjustment of the grid potential toward that of the anode, therefore, a point will be reached where a discharge will Occur between the grid and cathode. The pressure of the ionizable medium in the envelope 5 is of such value that the ionization and also the impedance in the grid circuit shall then effect a transfer of the glow or are discharge between the anode electrode I and the cathode electrode 4. In this manner, it is possible. to permit the electrons to have sufiicient energy to ionize the neon or other gas in the tube.

The effect of the discharge is to bombard the cathode 4 with positive gas ions, thereby heating it. This rise in temperature will cause the bimetallic cathode to flex so as to effect closing of the contact members I and 2. A very sensitive, quick-opening-and-closing thermostatically operated switch o1 relay is thus provided under the contr l of the control electrode 6. tor closing or otherwise controlling an external electric circuit connected between terminals l2 and I3. res ectivelv connected to the electrodes 4 andB. Such electric'circu t ma conta n any desired load. such as an electric si nal bell or other device 34, in series with a battery or other source of direct or alternatin potential 36 for supplying an output current. The np t current may be regarded as between the cathode and the grid.

The d charge between the anode, and the oathode resulting from the ionization of the gas produc d by the potential a plied to the electrodes efiects closing 01' the contact members I and ,2

' and conse uent operation of the signa bell 34 or other electrical control. Once thus closed, the circuit will rema n closed. and the tube will operate, independently of the grid, very much as takes place in a grid-glow tube. By appropriate means. however. the grid may be caused to stop the dischar e. instead of initiate it.

The discharge may be terminated, if the tube is operated from the battery II, by opening the plate circuit of th tube. or otherwise suitably reducing the anode potential. The grid, re aining control, will then again maintain conditions -to a point where the discharge cannot exist.

, A more convenient way, from this point of view, is to supply the energy to the tube from an alternating-current source 20, instead of the battery I I, as illustrated in Fig. 3. The discharge will then become extinguished when thevarying the Tirrill regulator.

der the control of a short electrical impulse. which may beused in connection with the grid to initiate the discharge. It is, therefore, adaptable for use in door bells or openers, gong ringers, burglar alarms, smoke alarms or indicators, industrial and traiflc controls, signaling devices. etc. It is adaptable, also, for temperature control, as a capacity relay, as a voltage regulator. and as a regulator for purposes similar to that of It may be'used, also, in tuned or resonant relay systems, as for carrier current control, as a time-delay relay, using the charging of a condenser in the grid or anode circuits, etc.

In Fig. 3, there is illustrated an application of this sensitive relay to operation direct from a photo-electric tube [4, having a cathode i8 and an anode IS. The alternating-current generator 20, as a source of power, is illustrated as connected between theca-thode strip 4 and the anode 7, through the impedance 9. The phototube I 4 may be connected as shown: its, anode It through an impedance I! to the grid 6 of the relay tube, and through an impedance Hi to the anode I of the relay tube; and its cathode [8 to the cathode 4 of the relay tube. These impedances may be capacitive, inductive, or resistive, or a combination of the same, but, for present purposes, they will be considered resistive. The

39 anode potential of the relay tube is adjusted to a high value, as described in connection with the system of Fig. 2. The grid 6 is caused to assume some intermediate value when light or other radiant energy, striking the phototube i 4, permits current to pass through the phototube. The relay tube can not then discharge. When the illumination on the phototube is reduced. sufllciently, however, the potential of the grid 6 becomes sufllciently near that of the anode I to cause the 49 discharge to take place, as above described in alternating-current voltage drops to zero or some other low value in an alternating-current cycle.

A tube of the described nature. besides beint very simple, inexpensive and efllcient, is capable larg amount of current. It has many applications where an electrical circuit needs to be closed upon the change of a voltage which is applied to the grid. when used on direct-current plate supply, it is particularly useful where it is desired that circuits be controlled un-.

connection with the operation; of the system of Fig. 2. This discharge causes the bimetal cathode 4 to become heated. effecting closing of the contact members I and 2 to exercise control over the external electric circuit connected to the contact members I2 and I3. Th s controlled circuit may. in turn, control an electromagnetic relay or a contactor of very large capacity, or the like, for such purposes as controlling street lights, or for the control of illumination in a room, where it is desired that lights be turned on when the level of illumination becomes too low. The street lights. for example, will become illuminated when darkness sets in, as determined by the photoelectrie tube l4. The invention is also applicable to other lamps desiredto be turned on and oil! by the action of light falling on the photoelectric tube I4, such as illuminating billboards, and for turning on lights at airports or beacon stations upon the arrival of nightfall.

A tube or this character has many advantages in its fields of application. One ofthe most important is that, as it is possible to position the contact members I and 2 normally or initially widely very far part, as by bending the bimetal strip into the position shown in Fig. 4, it is re ation of multiple-contact combinations. The

absence of a hot cathode renders unnecessary the required consumption or power to keep it ready for use in stand-by service. The life of the relay is relatively long, since there is nothing to wear out in stand-by service. The controlled current is much greater than that obtainable by ordinary cold-cathode tubes. Variations of the contact design, internal or external to the tube container,

such as using a mercury switch adapted to be operated by the bimetal, or a mercury pool into which the bimetal' dips a contact member, will provide even greater current and voltage control. The controlled voltage across the contact members is not restricted to the definite anode voltage of the tube, as in ordinary discharge relay tubes. The controlled current is not limited by cathode emission as in ordinary tubes. Since the engagement or the contact members takes place in an inert gaseous atmosphere, the contact members are weatherproof and dustproof, and no oxidation of the contact members takes place, as is the case with open electromagnetic or other relays. The cost of this .device, as, for example, is illustrated in Fig. 3, is very low compared to the cost of combinations of other devices performing the same functions. Sinc the cathode is heated considerably above room temperature, and since mercury need not necessarily be used in the tube, it is independent of normal external temperature variations. The relay will control and operate on alternating current without humming. Whether the tube is operated on direct or alternating current, it can control either direct current or alternating current.

In the systems of both Figs. 2 and 3, the rate of heating of the bimetal depends on the cathodeanode voltage drop, and the current that is allowed to pass through the discharge, as controlled by the ballast impedance 9.

Though the illustrated external control circuits have been described above as controlled by the closing of the normally open contact members I and 2, it will be understood that equally good results will be obtained if the control circuits described herein are maintained normally closed by normally closed contact members I and 2, and

are openedupon the opening of these contact members.

The tube may have also a stabilizing grid or other control electrode, as illustrated at 46 in Figs. 4 and 5. The control electrode 46 may be inserted about the glass tubing l5 encircling the anode wire I, inside the cylindrical grid 8. This stabilizing electrode 48, too, may be cylindrical and, like the control electrode I, it may surround the anode projecting from the glass iii. If connected into circuit as illustrated in Fig. 5, with the second grid 46 connected to the potentiometer it, through an impedance 48, at El, between the point of connection of the cathode and the point 2Q of connection of the grid, more stable operation of the tube will be obtained as regards breakdown and control by the grid.

Further modifications will occur to persons skilled in the art and all such are considered to be within the spirit and scope of 'the invention, as defined in the appended claims.

What is claimed is:

1. An electric-discharge tube having a gascontaining envelope enclosing an anode and a thermally-responsive cathode, and a control electrode therein for controlling a gaseous discharge between the cathode and the anode, said cathode comprising a bi-metallic strip.

2. An electric-discharge tube having a gaseontaining envelope enclosing an anode and a thermally-responsive cathode, a control electrode therein for controlling a gaseous discharge between the cathode and the anode, said cathode comprising a bi-metallic strip, and a contact member controlled in response to the flexing of the bl metallic strip.

3. An electric-discharge tube having. a gascontaining envelope enclosing an anode and a thermally-responsive cathode. a control electrode therein for controlling a gaseous discharge between the cathode and the anode, and a stabilizing electrode therein for stabilizing the operation or the tube, said cathode comprising a bi-metallic strip.

EDWARD CHARLES DENCH. 

